LCD devices are widely used as a TV screen or a computer monitor for desktops and notebooks. In general, LCD devices are driven by using techniques that alternate the polarity of the voltages applied across a cell. These techniques may include inversion schemes such as frame inversion, row inversion, column inversion, and dot inversion. Typically, notwithstanding the inversion schemes, a higher image quality requires higher power consumption because of frequent polarity conversions. Such LCD devices, in particular thin film transistor (“TFT”) LCD devices, may consume significant amounts of power, which may in turn generate excessive heat. The characteristics of the LCD devices will be significantly deteriorated due to the heat generated.
Charge sharing techniques have been developed in the art to reduce power consumption required by LCD devices. An exemplary column driver integrated circuit in the art uses multiplexers to selectively couple each of the columns to a common node during a portion of each row drive period. During the remaining portion of each row drive period, the multiplexers selectively couple voltage drivers to the columns of the LCD pixel array. In addition, the common node can be connected to an external storage capacitor.
Another power-saving circuit in the art uses switches and capacitors to passively change the voltage level on column electrodes without active driving by the column driver circuit. The power needed by the column driver circuit to drive voltages of alternating polarity onto the column electrodes is significantly reduced, particularly for the pixel inversion and the row inversion schemes.
The prior art techniques may save a significant amount of power in the column inversion and the dot inversion and row inversion schemes, respectively. However, these techniques in the art are not particularly effective in other schemes. It is desirable that a circuit is designed to achieve significant power saving in all the inversion schemes.